AERO 307: The Beginning (Week 1)

Although this was the final week of class, it didn’t disappoint. Our week began at 9:30 on Monday morning. We needed to get most of our flow viz done in the next three hours. We had spent almost all of our previous time getting our setup to sink. First, we started by putting our small cavity model in the tunnel upside-down. We had to put more weight on it (deja-vu) to make it sink more so that the entire cavity was underwater. We ended up needing almost 50 pounds. Since our ramps were two different sizes, we had to add a little more weight to the front. We first turned on the tunnel to 2 in/s and shot dye over just the gap. The flow did not separate over the 6 mm gap, as expected. We then filled the inner cavity with dye, and kept it running at 2 in/s. We noticed little to no change inside the cavity. The water was stagnant. There was very little escaping from the gap. We then sped it up to 5 in/s. We began to see some recirculation and an increase in escaping dye. This made sense with the increase in speed.

Next, we put the setup with the large cavity in the tunnel. Again, we had to weigh the whole model down with an incredible amount of weight. We also had to weigh down the front ramp to make it level. We turned on the tunnel at 2 in/s to see the flow over the gap. This time we saw the flow separate over the gap. This is due to the 5 mm vertical offset between the panels. We injected dye into the cavity, and watched at 2 in/s. Again, there was a little coming out of the gap but it was also stagnant. When we increased it to 5 in/s, we noticed it recirculating, and more dye was coming out of the gap, just like our last test. However, we noticed more coming out in both cases compared to the first test. This is expected because of the larger cavity and gap.

We ended up finishing around 12:30. We emptied the tunnel (very quickly) and went up to 322 to begin our presentation. Since we had worked on this project for so long, the presentation was going to be fairly straight-forward. We started by laying out an outline and then going back and adding details and pictures.

Between Monday and Wednesday, there was a lot of back and forth. We spent quite a bit of time outside of class working on the presentation, editing videos, etc. We met n Wednesday morning an hour early to rehearse. First to present were Sergio, Bob, and Louis. They talked about the bluff body design. I think it’s really cool to have a standard model for automotive testing. It really helps to simplify designs. Next, we were up. I think ours went very well. There were many questions that were asked, but I think we answered them all very well. After us were Yev, Will, and Matt. They worked on your project, the Lost Coast Surfboard Fin. It was a very well-done presentation, and they were extremely far in-depth. After them were Justin, John, and Derick with the hexacopter. I really enjoyed this one since we use a lot of the same components in DBF. Lastly, Hans, Alex, and Sam presented on Mobius winglet designs. I am actually really surprised that the round winglet was the one that performed the best. However, this does make sense at the low Reynolds number that they were testing at.

This week, I was involved in many things. I was the first one to get to the water tunnel and set it up. I filled it up and got everything ready for testing. I was the “man with the camera” so I acted as creative director for the flow viz. I told them how to adjust the model and dye to get the best film. I didn’t know how to edit the videos, so I passed them along to Bennett. After a rough outline was done, I ended up filling in most of the presentation with pictures and more details. I ended up presenting on the background and our models since I had a large part in both of them.

Some of our results were actually really interesting. The model with the larger cavity changed a lot of stuff. The flow over the gap ended up being turbulent due to the vertical offset. I actually didn’t expect this to happen due to the small size, but it makes sense that it did. We also got a lot more dye to come out of it compared to the smaller cavity.

Next week, I’m not doing anything for this class. I have two final projects and one exam, and I am done!

Today, Airbus announced that it will take over Bombardier’s C-Series aircraft division, effective June 1st. They will own 50.01% of the Canadian manufacturer’s latest line of aircraft. The C-Series never sold well throughout its run. It was seen as too big for a regional airline, but too small for a mainline airline. However, in the last few years, there has been a resurgence in the 100-125 seat market to reduce flying that the regional airlines have to do. However, when airlines went to purchase the C-Series, both Airbus and Boeing cut deals with airlines for their smaller aircraft. This sent Bombardier into a financial tailspin. Even though they got significant orders from Air Canada and Delta, they still couldn’t overcome it, leading to this Airbus takeover.  

Doig’s questions:

1.  I think the best thing I learned was how to make analytical decisions and conclusions based on just flow visualization. In previous classes and labs, conclusions were heavily based on numbers recorded and analyzed. In terms of a particular topic, I believe that I became really good at Reynolds number matching in this class. I was comparing things in quite a few labs, so that was crucial.

2. I think I am still a little confused at some of the higher-level equations needed for some aerodynamic calculations. A lot of the things were learnt in AERO 306, but we almost too hard to implement. This class was at a lower level, so using some high level equations in this context was hard.

3. I think the highlight of the class was getting to work on the Tesla Panel Gap Project. Being from Silicon Valley, Tesla has become a part of the region in the last five years with their headquarters and factory in the Valley. Additionally, Teslas have become the ultimate status symbol of people in the Valley. The Tesla problem has been sending shockwaves through the region, so it was awesome to help find a solution to the problem.

4. The lowlight of this project was probably the implementation of the Tesla project. We worked extremely hard to make our test setup. The ramps were cut to great precision and were sanded down to fit the model perfectly. However, when we put it in, they floated. We took around five hours to get it to sink, but it still wouldn’t. We totally underestimated the buoyancy of blue foam. At that moment, we realized that we would probably be better marine engineers than aerospace or automotive engineers. Blue foam can make anything float.

5. I honestly do not know where I see myself in the future. There’s many different things that I’d like to do in the aerospace realm, and even a few things not in the realm that I would like to do. I know that I wouldn’t really want anything that are heavy on the controls side, but I wouldn’t mind working on controls in a flight test or design context. I am heavily involved in flight test in DBF, and I will be working on satellite testing for Lockheed this summer, so I wouldn’t mind getting into that realm. 

Thanks for a great quarter Tynan!

Figure 1. Dye in the cavity of the smaller model. Notice that there is very little escaping.

Figure 2. Flow over the model with offset. Notice the separation after the gap

Figure 3. Flow over the Tesla model in the tunnel. The gaps aren’t too bad on this one...

Figure 4. Me showing the setup with the large cavity model during our presentation

*None of my anger is directed at you, Daniel, nor Dr. Doig. It is mainly at Tesla for not hiring enough manufacturing engineers and Archimedes for making a stupid principle.*

Since we had Monday off, our week began on Tuesday. First, we received confirmation that our second test model had been printed. We were all fairly busy on Tuesday, so we picked it up the next morning. The model had an offset in panel height and a large cavity in the center.

Later that night, we received an email from Daniel about our project. Dr. Doig had some recommendations for us regarding our project. The front angle of the ramp was too sharp, so the length had to be extended. The same thing applies for the back ramp, but it was ok if we left it as it is. All the corners on the ramp also needed to be rounded out. Since we were creating a whole new test setup with the next model, this wouldn’t be too much of a problem.

We began Wednesday by looking for some more blue foam. We needed a total of 4 ramps for two test setups. The two short ramps from the original setup would now be used as the back ramps for both setups. That means we still only had two ramps to cut. However, we only found a little bit of foam. We would have to be creative with how we cut the ramps. We wanted to make the ramps around 14.5” long, more than a 100% increase in length. We ended up cutting one to size and then only the sloped part of the second one, due to the minimum amount of foam in a single block. However, we attached a block of foam to the end to mirror the other ramp. The logistics of this actually took a long time, so we really didn’t have much time left.

We wanted to try to get in the water tunnel before next week, so we decided that we should test on Friday. We met at the water tunnel at 11 and got to work. First, we filled up the tunnel, anticipating an imminent test (Oh boy were we wrong). After doing some final sanding, we put the first test setup in the tunnel. Our dreams were quickly dashed when we realized that our setup was floating in the water. After wondering how that was even possible (with a few expletives), we decided that we needed to think it through. We realized that there was a steel plate next to the tunnel. It was double as thick as the aluminum plate we had been using and almost 4x heavier. It came to almost 4 pounds. We decided to mount our other test model onto that plate. However, after 30 minutes, the glue still would not dry. We then wanted to make sure that it would sink. We placed it on top of the model still in the tunnel. It still didn’t sink.

After this we were pretty mad. However, we still stuck through! We then actually glued the original model to the steel plate and added some more weight to part of the base of the model. It was close to 6 pounds in counter weight. Of course, it still floated. We then decided to go all out. We hollowed out a lot of the ramps and added a lot more weight. We were up to around 10 pounds, which was a lot compared to the weight of the setup, especially since the ramps were hollowed out. We put it in, and of course, it still floats. Hard to believe that so much weight on there still couldn’t make our model sink. We flipped the setup upside down and saw how it would work with the flow. We put some dye over it just to see how it work while upside down. We thought it looked fairly good, so we asked Daniel’s input. He agreed that this process would probably work. At that point, we were just about out of patience that day, so we decided to call it. After draining the tunnel, we realized that we had been there for just about 4.5 hours, with essentially nothing to show for it. Isn’t that great? Our future in the aerospace and automotive industry might be slim, but I think we might make a lot of money in the ship-design industry.

This week, I was responsible for getting the new model from the Innovation Sandbox and getting it ready. I picked it up on Wednesday for our tests. I helped design ramps for the new front ends and cut them using the CNC foam cutter. On Friday, I first did a lot of sanding—mainly the ramps and a little of the models. I also was the main operator of the water tunnel. I filled, drained, and operated it when on. I also ran around the wind tunnel and adjacent labs trying to find various supplies to try make our setup sink. I am also in charge of getting the videos of the experiment. I will use my DSLR to get video and Bennett will likely edit the video.

There were many things that didn’t make sense this week. The most obvious thing is the fact that 10 pounds of weight could not sink the test setup that we had. That is ridiculous. Our team knew that it would be light, but we thought that the original aluminum plate would hold it well. We thought that the ramps would hold some water and become naturally heavier. Further reducing the setup weight and increasing the counter weight seemed to do very little for us too.

Next week is the final week of class ☹. We need to test both setups, create a power presentation, and present it to our class and client on Wednesday. We are scheduled to go into the water tunnel at 10 on Monday, so hopefully we can actually get good flow viz. Just another day in 307!

Over the past few months, Rolls Royce has been under heavy scrutiny for their Trent 1000 engines. There have been reports of cracks in the compressor blades. A cracked blade has led to many incidents, likely including the Southwest Airlines flight in April. This had led to the grounding of all aircraft with the Trent 1000 which includes many Boeing 787 Dreamliners. This has sent many airlines in a whirlwind. The have had to cancel hundreds of flights around the world because of this issue. Additionally, they have called upon charter airlines to cover some of their flying. This has been one of the worse groundings in airline history, but thankfully, it looks to be getting better soon. This week, Rolls Royce announced that they have developed a permanent solution to the problem: a revised blade. They haven’t said any specifics, but they say that it will be manufactured quickly. They are going to test it on an engine statically this month, and on an airplane in the near future.

Figure 1. Our first test setup floating in the tunnel.

Figure 2. Me, sanding down a ramp for use.

Figure 3. A floating ramp and my reaction to it.

Figure 4. Bennett hollowing out the ramp to put in more weight.

On Monday, our Tesla Panel Gap group began preparing for our lab. Our preparation would end up lasting all week. We first visited the Innovation Sandbox to check up on our model. It turns out that they had not yet started the model yet. Luckily, I met my friend at the Sandbox, and he assured me that he would get on it ASAP. We then met up with Daniel to discuss the project some more. We realized that we needed to focus more on the ramps in front and behind the testing piece. We wanted to 3D print them until we realized how large they would need to be. We then considered using wood, but we couldn’t find enough scrap wood to make it work. However, we ended up finding a block of extruded polystyrene (blue foam).

At first, we were hesitant about using blue foam. Mainly, we were worried about the effects of water logging on the foam, and the resulting change in geometry. We broke off a small piece and ran it under water for a few minutes. We realized that not only did it retain its shape, but it was also free of any internal water. We knew that this was likely the way to go. We then took our block of foam up to the hangar. We used then used drew the ramp’ shape on DevFoam, and cut it using the CNC foam cutter. We made each of them seven inches long and 4 inches high, the same height as the test piece. When I got home on Monday, I found out that our test piece had begun printing.

On Wednesday, we began class by going down to the Innovation Sandbox to pick up our test piece. Originally, we were supposed to do our test on Wednesday, but we quickly realized that was not going to happen. It came out very well. However, it still had a thin printing base on there which needed to be removed and deburred. A trip to Cody’s office was in order. It took quite a while to get it completely done. After that, we went to the wind tunnel to do some practice testing. We knew that both our ramps and the test piece would float, so we needed to find a way to secure them to the bottom of the tunnel. We ended up finding a large aluminum plate that seemed to be a scrap. Josh and Bennett went to Mustang 60 to glue all three pieces onto the plate. Meanwhile, I worked on filling up the tunnel partially to see if our rig would float and make sure that water wouldn’t negatively affect our rig. We filled the tunnel to about halfway point. We fixed some issues with spacing and gaps and then drained the tunnel. We were going to begin testing, but then we realized we didn’t have much time left in class.

On Saturday, our Force-Balance lab group met up to finish our lab report. We had all been working sporadically throughout the week on it, but this was to finish it up together and make sure that we are all on the same page with it. I worked on the Experimental Background and Methodology and Error report. With our previous work, and the fact that we were all working diligently together, we finished in just under 3 hours!

This week, I was mainly involved in preparing for our Panel Gap Test. I mainly handled the production of our model. I sent it to the Sandbox and handled the post processing. I was responsible for setting up and cleaning up the water tunnel when testing. I also used my access to the CNC Foam Cutter to make accurate ramps for our test. On the lab report, I specifically worked on the experimental background and methodology. I also did the error analysis. I also helped a lot with the formatting of the report.

This week really put into perspective how big of a problem Tesla has with panel gaps. When I saw the finished model, I really couldn’t believe how big the gap was. I had to triple check to make sure that it was indeed the correct size (it was). I think our testing setup is actually very innovative. We used plastic and foam, but we will still get precise visualization due to the quality of manufacturing. I was also very surprised at how well the blue foam is holding up in the water. It did not get water logged and it retained its shape very well.

This week is very important for our Tesla Panel Gap project. We will be testing our model at some point this week. We also are printing a slightly different test part that has a larger cavity inside and a height offset between the gaps. We also need to start preparing for our final presentation as well. My force-balance lab is due later tonight, but we are mostly done with that.

This week Mitsubishi Aircraft announced plans to produce the MRJ70. This will be a smaller version of the MRJ90, a type that will be entering service within the year. This is actually a really important development for the company. This aircraft will hold 76 passengers, which is the maximum number for a regional airline under standard contracts. This will allow many regional airlines to replace some of their older aircraft. Many of the other regional aircraft manufacturers are no longer making aircraft at that size, so Mitsubishi is set to make a lot of money from this airplane.  

Figure 1. Our block of foam being cut into ramps on the CNC

Figure 2. Our finished testing model with the ramps and test section mounted to a metal plate and sanded smooth

This week was an important week in 307. On Monday, our group met at the beginning of class to discuss our Force Balance lab. Over the weekend, we had a disagreement on how many angles we should test at, so we needed to finalize our test matrix quickly. We decided that we would test at 0, 5, 10, and then every even degree up until 18. We also began writing some of the preliminary parts of the report in the little time we had left. Halfway through the class, we went down to the wind tunnel for the lab. Since Tynan wasn’t there, Kyle was supervising the lab. After a quick safety check, and wind-off/wing-off data collected, we fired up the wind tunnel to the first speed of around 19 m/s.

The first thing we did was collect wing-off data at that speed. We then sped it up to 25 m/s and took wing-off data there. We then turned the tunnel on and attached the large chord wing. This would be the one that we would run at 19 m/s. We then took wing-on, wind-off data, before turning the tunnel on. Then, we took wind-on, wing-on data (or just regular data). Running live time gave us a very typical CL vs. α plot. We then shut off the tunnel, detached the large chord wing and put on the short chord wing. Again, we took wind-off data before turning on the tunnel, this time to 25 m/s. Finally, we recorded our data for that wing and we were off for the day.

On Wednesday, we began our work on our final project. I was assigned to work on the Tesla Panel Gap project with Josh and Bennett. I originally had this as my second choice, but I am still happy that I got this one. Being from the Silicon Valley, I am happy that I can say that I helped fix one of the biggest problems in the region. Our day started with a conversation with Daniel. He and group of grad students have been working on this project throughout the year and have reached an impasse on this decision. Tesla has told Cal Poly that they are seeing air come out of the gaps, and they don’t know why. The grad students have experimented and debated as to why this is happening, and they can’t really decide either. They want us to come to our conclusion so that they can make theirs.

First, Daniel explained the project itself, and how wed be contributing. He sent us the CAD file of the testing piece that we will use. The gap is only 4 mm, so it must be done perfectly. Inside the gap is a cavity where air likely recirculates. After Daniel departed, we worked on our test plan. We were going to recreate their gap model, but in the water tunnel. We will make it span the width of the test section, so push one side onto the glass, so that we can see inside the cavity. We will run the tunnel at a very high speed. We will not be able to match Reynolds numbers, but we will get a somewhat smooth visualization at faster speeds. As a stretch goal, we will look at the gap on its side, and see how that affects it. We adapted the model that the grad students sent us, and I sent it to the Innovation Sandbox for printing a few days ago.

This week I worked on a lot of stuff. First, during the wind tunnel test, we each got to perform different tasks. I recorded data on our new data logging system. I also was responsible for attaching the wings onto the mount and made sure that they are level. I made sure that the wing stopped moving each time before we took data too. On Wednesday, I helped write the test plan in addition to brainstorming our setup for the experiment. I am handling the printing of the model and some of the finish of it too.

Seeing the data from the force balance setup was actually really cool. Our drag data seems to be a little wrong, but apparently a lot of people are in the same place as us (right trend, wrong numbers). The Tesla panel gap project is much more puzzling though. The grad students say that there is air coming out from the gap, but I can’t tell why. I’m guessing that air goes into the cavity from the gap, recirculates, and comes out. This will definitely be something that we will need to look at later.

This week is a big week in 307. With our force-balance report due next Monday, most of the work will be done this week for that. Most of our preliminary analysis is done, but we do need to write most of the report. This week will also be the week for testing our panel gap model in the water tunnel. We need to have the model printed, sanded, and clear-coated before putting it in. There is a lot of work to do, but there will be enough time to do it.

This week, Boeing received FAA certification for the folding wingtip on their 777X line. This is a ground-breaking step for commercial aviation. The 777X series has a larger wingspan compared to current 777s. In order to fit in the same gate space, Boeing had to fold their wingtips in order to make them fit in the same square footage on the ground. This will be very helpful to the smaller airports that get 777 services. The original 777 was meant to have folding wingtips but was not implemented by Boeing. In fact, the first ~150 777s are setup to fold their wingtips, but Boeing did not install any mechanical systems to do it. After that, Boeing stopped putting that setup in there. This could easily pave the way for many other folding wing designs in commercial aviation.

Figure 1. The force-balance setup with the large chord wing

Figure 2. The small chord wing with tufts for flow-viz

Figure 3. Our CL vs. Alpha plot. This follows a standard plot, and backs up our findings. 

This week was the most “chill” week that we have had so far in the class. Our first day was spent listening to Flow Viz presentations. I really liked all the presentations that we saw. First was Bob and Sergio’s submarine presentations. I thought that they used the water tunnel the best (besides us) because they actually put an aquatic vehicle in the water. I really saw a connection from their findings to how aircraft fly with the same stabilizers. Next was Derick and Louis. They put a large F-16 in the wind tunnel. I couldn’t believe the amount of effort that they put into making their model. I really wish I could put that in my room 😊. I think it was really cool that they recreated the odd vortices on the mid-fuselage of the plane. It’s a very odd design decision, and the dimensions had to be perfect to make it work.

The next group was Josh Matt, and Bennett with their baseball-on-a-stick. They put it in a water tunnel and looked at the effects of spin on the fluid around it. As a die-hard Giants fan, the last ten years have been defined by great pitching, so visualizing the science behind these spins was really awesome.  Then was John and Will. They attached a mini football to a mechanism to make it spin and then put both in the wind tunnel. They really mimicked the typical spin that a football sees in an NFL pass. It really showed how well the football is aerodynamically designed. For both of these projects, I wondered how much the seams influenced their findings, but I didn’t get to ask in class. I will be sure to ask them in class this week.

Alex and Hans were the second to last group to present. They discussed winglet design as a research supplement for Project Mobius. I have helped them with wing construction before, so it was cool to see an update on the project. I am also a big fan of the effects of winglets and their design, so it was really cool to see it. Finally, the best group gave their presentation. Yev and I presented our findings on the visualization of flow in the water tunnel. I thought out presentation went really well. I think we had a very in-depth look at flow visualization over the aircraft that we created. However, I do think that we went a little too far over time, but that was likely because we had too much information to share. We also thought that some of our vortices were caused by the flow over the airplane, when they were actually caused by the turbulence from the wand. However, we did mention that in our list of assumptions and problems.

Wednesday ended up being a much calmer day. Our group met to discuss and prepare for our force balance lab on Monday. First, we made a test script for our data. We made a function to account for the wind-off and wing-off data and then will run it with each data list that we get. After that, we worked on our first XFLR models. Before that, we needed to figure out how the program worked. After we did that, we played around with the software to try to figure out how to import a wing. This took longer than we are willing to admit, which was basically the rest of the class period.

On Monday, I presented my findings on the Boeing 777 flow visualization. I helped do the experiment, the slideshow, and the explanations. I also listened to all the presentations to further advance my own knowledge on flow visualization and aerodynamics. On Wednesday, I helped work on the test script for our lab. I also helped with figuring out XFLR and tried to get an idea on how to operate it.

I definitely found many of the presentations very cool. I think the best one was the F-16 model in the wind tunnel. Just the overall construction of the aircraft was amazing. Then, to actually put it in the wind tunnel and get some of the same effects that NASA got was really cool. I thought ours was actually really nice too, since we had some very distinct vortices.

On Monday, our group will probably work on XFLR a little more before going to do our force-balance lab. We will test at 10 angles of attack, with an emphasis towards still. We will also test at two different speeds but match the Reynolds numbers. I guess I will also begin planning for our final project this week as well.

This week, Airbus and Rolls-Royce teamed up to demonstrate their UltraFan engine. It has been re-geared and has an “advanced core”. The bypass ratio is much higher than the current Rolls-Royce Trent 800 engines, and it will burn around 25% less fuel. The current engine will likely be fitted on the Boeing MoM (150-250 seat airplane) but the technology will be applied over all of Rolls-Royce’s new engines. Ironically, this engine will be tested on a Boeing 747-200. This is Rolls-Royce’s aircraft so it makes sense. Airbus has previously done testing for Rolls-Royce on almost every widebody aircraft that they have produced.

Figure 1. Yev and I modeling our outfits after our presentation

As the title says, this week was devoted mainly to analyzing our flow viz projects. For Yev and I, this was no different. We decided that a PowerPoint presentation would likely be the best way to present the data. The first thing that we did was watch the raw videos from both cameras and highlight specific parts of our test that we want to talk about in the presentation. After watching all the videos, at both angles of attack, we narrowed down the list to: engine, fuselage, tail, wing, and wingtip. After we had those two things, we split up our tasks. I began creating the presentation. I worked on the background, both scientific and historical. In addition, I worked on the test overview slide. Meanwhile, Yev went through the videos, edited them, and rendered them for viewing. He slowed the videos down to 1/8th speed and put the top-down view side-to-side with this.

After he was done with the videos, we again sat together and watched each of the edited videos many times at different speeds. We did this in order to find interesting things to talk about, and how to scientifically explain them. Watching at such a low speed gave us time to really see the intricacies of each of the types of the flow. We also wanted to compare both flows together, and the slow-motion version helped.

The flow over the fuselage at 0 degrees was very normal. We did get to see the flow completely stagnate at the root of the wing, indicating a region of higher pressure. It also created a large wake, which was expected. At 15 degrees, the flow was forced above the plane due to the AoA. We also got a weird recirculation at the trailing edge of the root.

The flow over the engine was as expected. At 0 degrees, a wake immediately starts after it hits the engines. The flow travels along the engine rather than going above or below. This isn’t too good of a representation because theoretically the engines would be on. At 15 degrees, you can start to see some flow going over the wing. This flow ends up separating there, so we know that the aircraft is past its stall angle of attack.

At 0 degrees, the flow over the wing yielded small von Karman vortices. They weren’t really the easiest to measure, but they were apparent. When the AoA was increased to 15 degrees, the vortices could easily be seen. This was because the flow that went over the wing separated at the leading edge. This is another reason to believe that the aircraft stalled.

When the dye was shot over the wingtips, vortices were extremely noticeable. This yielded a Strouhal number of 5.76. This is probably the most accurate number that we could get. However, this still is much higher than usual. Due to the small nature of our experiment, the number is probably not accurate. When at 15 degrees, the vortices converge into a wake just after the wing. This is showing that the flow is more turbulent. We also briefly looked at the flow over the tail. The tail created some sideways vortices (the tail is basically an airfoil). We also noticed some flow moving up the tail. This might just be a surface tension issue.

Personally, I worked on a lot of the PowerPoint presentation this week. I wrote most of the slides and did the compilation of the information. Yev worked on the pictures and video editing. We both did the analysis, with most of the background information coming from me.

There were a few things that we found interesting and odd. First, the flow over the fuselage at 15 degrees resulted in a vortex generated at the root of the trailing edge of the wing. This might be due to surface finish, but I also think it might have to do with the non-straight flow over the fuselage. The flow also moved up the tail when the flow was going there. I am fairly sure that this is just due to the surface finish. I knew we would get wingtip vortices, but I didn’t expect them to look so apparent and cohesive. In addition, we didn’t expect to see so clearly the effects of stall.

Next week will start off with our Flow Viz presentation. Then we will begin talking about the force balance experiment. I don’t have any ideas for that just yet, but I hopefully plan to have that within the next few days. After talking with my new group, I’m sure that we will discover something that we want to look at.

Yesterday, a ULA Atlas V (supposedly) launched from Vandenberg (I heard no one could see it with the fog). It carried the Mars InSight lander, made by the fantastic Lockheed Martin Space Systems. It will examine the surface and the interior of the red planet. Additionally, MarCO CubeSats will be deployed to relay information from Earth to the InSight and vice versa. The MarCO project was partly developed by Cal Poly and my space systems professor, Dr. P. This project really involves me, especially for a satellite.

Figure 1. Flow over the fuselage at 0 degrees. Notice the high pressure area at the root leading edge.

Figure 2. Flow over the engine at 15 degrees. You can that see the flow that goes over the wing separates, indicating stall.

Figure 3. Flow over the Wing at 15 degrees. Again, we can see the flow separating, indicating stall.

Figure 4. Flow over the wingtip at 0 degrees. Notice the extreme prevalence of the von Karman vortices.

This week was probably one of the most important weeks in 307 so far. Our first lab was due and we had to perform our second experiment. The work week began on Monday.

When we came to class on Monday, our first task was to familiarize ourselves with the (water-filled) wind tunnel. We first figured out the operation before we did anything else. We learned about how to control the flow and what safety precautions we should take. We learned how to control the speed and the dye. We wanted to use the red dye, but we couldn’t get it to work properly. Because of this, we had to use the green dye, which really wasn’t too big of a problem. We then used the hose to fill up the tunnel. After filling to an appropriate height, we turned on the tunnel for a few minutes and tested the dyes. Since there were six of us (two groups), it didn’t take too long to drain the tunnel.

After that, we went to the Innovation Sandbox to check in on our models. The 747 SCA model had finished printing. However, it did not come out very well. The Space Shuttle came in many layers, and we did not want to put it in the tunnel. We then asked them to get started on the 777, which we would need for Wednesday. We chose silver PLA to make it stand out, and it began printing while we were there. We then went to 322 to work on our “infinite” wing labs. Mine was due on Wednesday, so it was crunch time for our group. I only got back to the classroom with a few minutes left in class, so there wasn’t much time to work on the lab report. My other group members were also busy planning and working on flow viz, so we didn’t really get too much stuff done in class.

That night, I worked on finishing up the analysis of our lab. Although I had already written and talked about it, I hadn’t actually done it on the lab document. With that, our lab was very close to being done. We only had a few sections left, but none left were mine. On Tuesday night, I got a knock on my door. The student at the Innovation Sandbox, who is also my neighbor, came to hand-deliver our completed Boeing 777. It came out very well. Even the people at the Sandbox couldn’t believe how well it came out.

The next day, we went into the wind tunnel with our model and only a few ideas on how to attach it in the wind tunnel. After many ideas, we finally decided to tie it with two strings to a metal plate and let it “float” in the water. In order to change the angle of attack, we would just tie the back string tighter and decreases its length. After figuring that out, we went back to the classroom for a few minutes to work on our previous labs. My team was all done with their sections, and then started proofreading. I helped them with that and made corrections until it was our time to use the water tunnel. It took a while to drain and refill the tunnel since it was our first time, but eventually it was. We then setup three cameras: a GoPro behind the plane in the tunnel, a GoPro on top, and our phone from the side. We did it at 3 in/s and a very high dye concentration. We realized that we did not get too good of video due to the high dye concentration, so we decided to come back the next morning. On Wednesday night, we finished our report after a lot of formatting and proofreading, so hopefully, it is up to your standards!

On Thursday morning, we began testing at 9 AM. We changed our camera setup on Thursday. We put a GoPro up top and on the side. We eliminated the one in the tunnel due to lack of clarity. We quickly filled the tunnel and began testing. Since our first test was at a 0-degree angle of attack, we decided to start with 10 degrees. We upped the speed to 5 in/s and made sure that the dye was on a lower setting. We got very good results while doing this. The flow over each of the parts of the plane was very clear, and most things were expected. We could see some of the wake after the wing, and the size and direction made sense. The only problem we were getting was the non-straight dye hitting the plane. I moved the dye stick further up to the plane to diminish this effect. After the water became too cloudy, we quickly drained and refilled to test again. We decided that 5 in/s should be the speed of operation. We then changed the angle back to 0 degrees to repeat what we got the day before. We got very good results again, and different from the previous run, so we knew that changing angle of attack actually did something. There was the expected flow over the wing, the nose, and the wingtips.

Personally, this week, I did a lot of the analysis of my lab report. I also helped proofread and format it once it was finished. Again, I was in charge at getting the models ready from the Innovation Sandbox and making sure that they were ready to go. I had to sand the wings to make sure that the finish did not have an effect on our visualizations. I was the one who was filling the tank while Yev got the cameras and the models set up. During the tests, I was the one controlling the amount of dye and the placement of the wand. We both did the cleanup by scooping water from the tunnel.

One thing that we didn’t really understand was the flow over the nose in the 10 degrees angle of attack. The flow would go over the wing, and then drop down to the wing at around the half-chord. It would then recirculate after it went off the wing. We didn’t know why this was. We think that it could have been from the string or from the surface finish, but we will review the video and research it and hopefully find something. I was actually surprised at how well the model worked. We could see much of the expected patterns that we have seen in previous test and images. Even with the very small scale, we got a lot of detail on the model, which likely contributed to it.

Next week, we need to go through the footage and find what we want to use for the presentation. We need to research some of our findings and make some conclusions. We also need to actually create the presentation and rehearse it for next week.

This week, Virgin America ended their operations after 11 years of service. They are merging with Alaska Airlines in their quest to become the “West Coast’s Airline”. Being from the Bay Area, Virgin America was my hometown airline. I flew them over Spring Break as my farewell to them since I couldn’t go on their last flight. It was really awesome to fly them one last time before they flew off into the sunset. Virgin America flies Airbus A319s and A320s. Recently, they got A321-200neos (neo = New Engine Option). This airplane was not only a large seat upgrade but also in aircraft efficiency due to new engines, winglets, and interior weight savings. I actually got to fly it on one of my legs. The airline will definitely be missed!

Figure 1. Controlling the wand and the dye strength

Figure 2. Our camera setup with the dye going over the wingtip We can see the typical tip vortices come off.

Figure 3. Flow over the nose and some over the root of the wing

This week was the least hands on that I have this quarter so far. Nevertheless, the paperwork is just as important. On Monday, we finished up the analysis for our wake study. We made our final plot of the wake study with all 6 runs (Figure 1). The graph was basically what we expected.

We expected the physical location of the wake to be a generally lower number as angle of attack increased. This is basic geometry. However, when comparing this data with that of the trip strip, we found a few interesting items. First, it seems that for each of the runs, the data with the trip strip had an increase of position mm by around 5-10 mm. This actually makes sense. In addition, as the angle of attack increased, the minimum value of CP also decreased When the trip strip is added, the flow stays attached to the wing for longer, causing a smaller wake at the same angle of attack. In addition, we are also getting lower values of CP with the trip strip compared to without at the same angle of attack. Although the trip strip reduces the size of the wake, the amount of drag generated is still very high. This led to the lower values of CP for those runs.

In addition, we also began to discuss our next lab with our new group members. My partner, Yev, and I had previously discussed the groundwork for our lab, but we just brainstormed a little more on what we specifically wanted to look for.

For the rest of the day, we worked on our lab report. I finished up the methodology and began writing some of the results. In addition, we also added all the necessary plots and diagrams that we will be using for the lab report.

On Wednesday, I formally met with Yev to discuss our next test. The week before, we sent a Boeing 777 and two Boeing 747 Shuttle Carrier Aircraft (SCA) models to the Innovation Sandbox to be printed. We first had the idea to put something in the water tunnel last week but didn’t know what. With my background being commercial aviation, I knew I wanted to put some sort of airliner in there. After thinking of all the possible choices, I narrowed down on the Boeing 777. This was due to an incident that took place on March 8, 2014. On just a routine night, Malaysian Airlines 370 departed Kuala Lumpur, bound for Beijing. However, no one would hear from it nor the passengers ever again. One conspiracy theory is that the plane might have flown underwater (stupid, right?). In order to debunk this, we will put the 777 in the tunnel and see its effects. In addition, Yev also wanted to put a model of the Boeing 747 SCA in the water because it looked cool and he wanted to keep it afterwards. I also wanted to keep one afterwards, so we asked the Innovation Sandbox to print two for us.  

One thing that was really didn’t really understand was how the setup of the water tunnel would be. More specifically, we did not know what to specifically test for. We knew that we would shoot dye at the plane, but how would we quantify this. In the end, we decided on changing the angles of attack of the models. We will first do the test at 0 degrees and then change it to 10 degrees. We really want to focus on the leading edges of the tail, the horizontal stabilizer, and the wings. We also want to see the effects of the dye hitting the nose head on. As a push goal, we will test the 747 SCA with the same conditions. We wanted to do two different speeds (5 and 2.5 in/s), but we advised against it due to the similarity in speeds. As of now, one model is completed. Both other models should be done early next week. We planned to test on Wednesday from 4 to 6, so hopefully they print in time.

This week, I worked a lot on our lab report for our infinite wing tests. I expanded on the methodology and added more to the results section. I also worked a lot on getting stuff set up for the flow viz experiment. I got all the models printed at the Innovation Sandbox after finding them online. I also wrote the test plan for next week.

I found our insights on the wake data to be very interesting. I expected the graphs to each have the same magnitude, but just shifted over. I did not expect the magnitude of the CP plots to change with angle of attack and with the trip strip. One thing that we didn’t really understand is how to attack our models in the water tunnel. After speaking with a 307 alum, we learned that we might be able to attach it outside the tunnel and then hold it in. This will be a challenge.

On Wednesday night, our lab report is due. I am not too worried about finishing it, but there is a lot of work and perfecting that needs to be done. I’m sure with a solid effort for our group, it shouldn’t be too bad. On Monday, I have to check out the water tunnel and make a final determination on how to mount our model. On Wednesday evening, I am doing our flow viz tests. I need to make sure that I have the model ready to go for it.

This week was Design, Build, Fly’s California Flyoff. We were supposed to go to Wichita for our worldwide competition, but due to California Regulations, we could not travel there for this event. Instead, we decided to host a flyoff with other public California schools who couldn’t go. This year, the goal of the competition was to build a plane to carry passenger (bouncy balls) and cargo blocks. Since our score was divided by wingspan, we decided to build the smallest wingspanned aircraft possible. We built a “Rectawing”, an aircraft with no fuselage and a 10.25” wingspan. In the end, we did amazingly well, and beat the only other competitor (San Jose State).

Figure 1. Wake Data from Last Week

Figure 2. Our 777 Model

Figure 3. Our 747 SCA Model

Figure 4. One of our aircraft being printed. (Photo: Innovation Sandbox--Alex Decker)

My second week began on Monday April 9th. My group was not testing, so it was entirely spent in class. We started off my finishing the analysis for the first part of the lab. We noticed that we were getting some incorrect values for our CD plot, but apparently this is consistent with our data, so we left it alone. We realized that adding the trip strip only increased our stall angle by about 2 degrees, much less than planned. We also worked on corroborating our results with data from Xfoil and previously used panel code. I also began writing the lab report. I correctly formatted the template and wrote the introduction.

On Wednesday, we began class by listening to Kyle’s lecture about wakes and getting wake data in the lab. This was especially useful since we were testing later that day. We learnt some of the basics of the traverse and the types of graphs that we should look for. Originally, we wanted to test at 5 different angles (-5, 0, 5, 10, 15 degrees), and then one measurement with the trip strip if time permitted. However, with Kyle’s advice, we decided to test only at 0, 5, and 10 degrees. As a time-permitting push goal, we wanted to test at 5 degrees with our trip strip.

In the few minutes we had between Kyle’s lecture and our scheduled lab time, our group went over our code for the wake test. I also worked on the lab report. I added more content to the lab report. Specifically, I finished the methodology up to the wake test. A few minutes before it was our turn to test, we went down to the lab.

When we got to the lab, we familiarized ourselves with the traverse and its control. We learnt that the traverse position at the middle of the airfoil at 0 degrees was at 331 mm. It was our job to then decide the ranges for each angle of attack. Our TA advised us on which values to choose for our initial test, and then we could decipher the values for the rest of the tests. For each test, we made sure that there was at least 5 mm on either side of the wake profile. We initially decided to increment by 2 mm in the freestream and by 1 mm in the wake, but we ended up just doing 1 mm throughout. After running the tests on 0, 5, and 10 degrees, and getting very good data, we realized that we still had around half the time left. We decided to test our trip strip at the same angles that we previously tested at. We made sure that we fully captured the wake for each run with enough freestream on either end. Since we were updating our plots on the fly, we could see if a data point looked out of place. If it did, we could just go back and remeasure at that point, and usually, it would correct itself.

Later in the week, I started planning my next project. Yev and I will likely use the water tunnel to build on a conspiracy theory in aviation. I already sent models out to be 3D printed.

This week, I worked a lot on our lab report. From my group, I was the only one to start. So far, I finished the introduction and have most of the methodology done. During the wake testing, I mainly operated either the wind tunnel or LabView. When not doing either, I was helping analyze our output graphs, and make sure that they had the correct shape and value. I also took some pictures for the report and my blog posts. I worked a lot on the next lab in the last few days. First, we discussed what type of experiment we want to run. Then I found models that we could use in the water tunnel and sent them off to the Innovation Sandbox for printing.

I was very surprised that the trip strip only changed the stall angle by about two degrees. I expected the difference to be closer to 5 at the least. The CP was lower at the place of the strip and a little behind it, but other than that, there was not much of a difference. I understood most of the stuff, but I think our group needed a little help with finding our CD total. We think we should add them together, but we aren’t too sure.  

During this upcoming week, I need to figure out the specifics of the next lab. Although we know that we will put the models in the water tunnel and use dye, quantitatively, we do not know what to look for. We will need to determine our full test plan this week. I also need to wrap up the lab report of the last lab. Although I have done a fair amount of work on it, there is a lot still to be done.

Out in Colorado, Bye Aviation’s Sun Flyer 2 made its maiden test flight. It plans on being one of the first mass-market electric General Aviation planes. It is aiming to be the go-to aircraft for flight training. They are estimating that it will only take $3 per hour to run, which would be a tenth of what is needed to keep Cessna 172s running.  The batteries have a 260 W*hr/kg allowing a fairly large range of the aircraft. The hard part about this will be getting FAA-certified. However, once they do, they could easily take the market by storm.

Figure 1. Cl vs. Alpha. Notice the similarity

Figure 2. Cp with a trip strip. Notice the dip at and after the quarter chord. 

Figure 3. Our setup for the wake experiment.

Monday began the final quarter of my third year at Cal Poly, and it started with AERO 307. After meeting in the Wind Tunnel Lab and going over some of the specifics of the course, we moved to 322 to prepare for the first lab. After sitting with the group and tossing around ideas, we decided to analyze the difference between the flow over a normal wing and the flow over the wing if the flow was tripped, using some sort of rough surface on the upper edge. We then decided to analyze the differences in stall angle. We would take pressure measurements at many angles of attack and use a CL vs. alpha plot to show the stall angle of both the tripped and non-tripped wing.

 After inspection of the wing, we decided that the ideal place to trip the flow would be between ports 8 and 9 on the wing. Ideally, we wanted the flow to be tripped just prior to the max thickness of the airfoil (upper end of the leading edge). We figured out that it should be between ports 8 and 9, which measured to be the quarter chord of the wing. We also decided to used 200-grit sandpaper to trip the flow, citing that it was rough enough to just trip the flow, but not to completely disrupt it. We agreed to test at every other angle, with each angle closer to the expected stall angles.

 On Wednesday, we went to the lab for the experiment. We didn’t think that 200-grit sandpaper would be rough enough, so we used 100 instead. During the lab, I operated the wind tunnel, LabView, and changed the angle of the wing for different runs. After we took our pressure measurements on the wing without sandpaper, we attached a .5-inch wide strip of sandpaper long enough to cover the locations of the ports. We taped it outside of the port locations. When we turned on the tunnel, we heard a lot of flapping and realized it was the sandpaper. After searching the lab, we found tape used to protect flooring from high traffic areas. It is very similar to sandpaper and had adhesive the whole way down. After attaching that, we had no problems with the rest of the experiment.

 Personally, I helped a lot with the initial ideas of the lab. I helped with discovering our experiment, and finding the necessary data needed to perform it. I also helped a lot with the test plan itself. During the lab, I operated the wind tunnel, LabView, and changed the angle of the wing for different runs. I was used our panel code, creating in an earlier class, to compare our data with what was generated in class (See Below).

 The stall angle for the tripped wing was very odd. Initially, we only expected to go up to 18 degrees for both runs. However, while plotting the data, we noticed that the tripped wing had not yet stalled when we reached 18 degrees. We went up to 20 degrees, and noticed that it stalled around 19, so our extra data was needed. Since this experiment was fairly standard, there were no huge insights.

 This week, we will continue our analysis on part 1 of the lab. We still have to do our CL and CD plots for both runs. We will also begin to write our lab report. Most of it can be done before the next part of the experiment. On Wednesday, we will perform the second half of the experiment—the wake study.

 This week saw the launch of the Lockheed Martin/NASA supersonic aircraft. The main part of this x-plane is to reduce the noise effects of going supersonic. Although this doesn’t apply to 307, it definitely applies to 303. This technology could then be applied to commercial aircraft and would likely change the dynamic of commercial aviation as we know it.

Figure 1. The wing with the new trip-tape on it

Figure 2. Using Panel Code, I created this graph of the Cp vs. Wing Location all all angles of attack without the trip strip.

Figure 3. Cp vs. Wing Location with no Strip from the Data